共查询到20条相似文献，搜索用时 140 毫秒
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甘肃桦树沟（式）铜矿床成矿条件与成因探讨 总被引：7，自引：0，他引：7
桦树沟铜矿床是近年来在甘肃走廊南山下古生界变质火山—沉积岩系内硅铁建造中新发现的一类富铜矿床。通过对该矿床的地质特征和一系列测试、分析数据的研究对比,认为该铜矿属海底热水沉积(变质)—后期热水迭加改造成因,并总结了桦树沟(式)铜矿床的成矿控制条件和找矿评价标志,认为在走廊南山中段下古生界硅铁建造中具有进一步找桦树沟式铁铜型铜矿床的良好前景。 相似文献
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冀东地区元古宙多金属硫铁矿矿床地质及其成矿作用 总被引：4，自引：1，他引：3
通过对冀东地区元古宙多金属硫铁矿床成矿构造环境背景、喷气沉积岩地球化学以及矿床中大量矿化嗜热微生物的发现与研究 ,以及采用分子生物学对沉积记录中的生物标志物的研究。得知冀东地区多金属硫铁矿的形成主要由海底喷气沉积与嗜热微生物富集成矿作用所致。运用海底喷气成矿热流体活动 嗜热微生物吸附与新陈代谢 多金属硫铁矿床形成的成矿理论 ,指导该区硫铁矿找矿工作已见成效。 相似文献
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驼路沟喷气沉积型钴（金）矿床成矿地质背景及矿床成因的地球化学限制 总被引：2，自引：1，他引：2
驼路沟矿床是东昆仑南部造山带中新发现的钴(金)矿床,它的含矿岩系是一套浅变质的(绿片岩相)震旦-寒武纪火山-沉积岩系.火山岩是一套中-酸性凝灰岩及熔岩,其元素地球化学特征类似于活动大陆边缘或弧火山岩;沉积岩包括碎屑岩和黑色页岩,它们具有活动大陆边缘沉积岩的元素地球化学极性,部分沉积岩具有现代大陆弧地区沉积岩的元素地球化学特征.岩相学、矿物学及元素地球化学研究证明,作为主岩之一的石英钠长岩是典型的喷气沉积岩,而并非"脉岩",它不但是钴(金)矿体的重要找矿标志,而且也是喷气沉积矿床的重要鉴别标志.钴(金)矿石组构及矿石矿物的世代显示其主要与海底喷气沉积成矿作用有关,在后期的碰撞造山过程中,受到了改造和活化.矿石和喷气沉积岩的痕量元素地球化学特征表明,它们同属喷气-成矿流体较远离喷气中心的海底沉积物.总之,岩(矿)相学及元素地球化学资料证明,驼路沟钴(金)矿床主要属喷气沉积矿床,形成于震旦-寒武纪东昆仑南缘的活动大陆边缘环境. 相似文献
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Large scale segregation of sialic crust from mantle material may have taken place by magmatic differentiation, partial melting or by exogenic processes. Weathering is a little considered, but verifiable process by which free silica can be generated in quantity from mafic material. In proto-Archean time acid ocean water must have been highly reactive. Even submarine weathering by such acid water could lead to large scale generation of free silica. Evidence from soil formation supports this view. Recrystallization of weathering products would take place by anatexis in the course of relatively intense recycling processes in pre-Archean and early Archean times. Much Fe and Mg in shales and carbonates would segregate downward as mafic xenoliths. The sialic fraction would be returned to shallow crustal levels by diapiric ascent and upward melting. This model is valid only if the sialic crust has grown little since Archean time. We show that “primitive” isotope ratios in later sialic rocks which may suggest gradual accretion of sialic crust throughout geologic time can also be explained by recycling mechanisms. We conclude that exogenic processes in pre-Archean times could have generated most of the sialic crust. 相似文献
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A. P. Jones 《Geology Today》2002,18(1):23-25
Archean serpentinites in the Komati river valley, South Africa, have distinctive crystal textures and volcanic features which distinguish them from normal coarse-grained serpentinites. They are interpreted to represent peridotite lavas erupted into a deep submarine environment. 相似文献
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冀东地区金矿床大多产于太古界迁西群金厂峪组斜长角闪岩中.具有明显的层控特征.金厂峪组斜长角闪岩原岩为一套海底基性喷出岩.通过金厂峪组斜长角闪岩的岩石地球化学特征、岩石含金性、载金矿物及微量元素特征和金的溶滤实验、同位素数据资料的分析,结合野外宏观地质特征.阐明金厂峪组斜长角闪岩是冀东地区金矿的矿源层. 相似文献
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华北板块北缘太古代的地体由连续性很差的表壳岩及其他变质深成岩构成,即原建平群的一部分。不连续的表壳岩原岩为一套夹硅铁质的基性火山岩-火山沉积岩建造,为高级变质区的古老绿岩残块。在太古宙晚期遭受了强烈的造山运动改造,发生了变质与变形。本次在1∶25万阜新市幅、鞍山市幅区调修测工作中,通过野外地质调查、岩石地层学研究、造山带地层研究和同位素测年,以及原岩建造和地球化学研究,将研究区内这套中、深层次变质表壳岩,从太古宙原建平群中解体出来,建立小塔子沟岩组,划归为新太古界。 相似文献
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卡瓦布拉克大断裂北晚太古宙喀拉塔格南岩群,为灰色片麻岩系(TTG岩系)及二长-钾长花岗片麻岩系组成的高级变质区,后者常呈脉状或不规则状分布在TTG岩系中,构成灰、红相间的景观特征.岩石具高角闪岩相-麻粒岩相变质特征,发育中深层次的塑性流变变形,变质矿物有反条纹长石、钾长石、角闪石、铁铝榴石等,区域上还可见蓝石英、紫苏辉石、硅线石.经岩石化学研究,组成该岩群的片麻岩具英云闪长岩-奥长花岗岩-花岗闪长岩(TTG岩系)组合特征.该套变质岩系可与库鲁克塔格、尾亚、阿尔金等地太古宙中深变质岩系对比,时代厘定为晚太古代较恰当,构造属性为塔里木地块的前震旦纪结晶基底. 相似文献
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Shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central Fennoscandia 总被引：1，自引：0，他引：1
We analyze splitting of shear waves recorded during the SVEKALAPKO passive seismic experiment in south-central Finland to study fabrics of the mantle lithosphere of the Precambrian region and thus to bring information into a debate on existence of plate tectonics or its forms in the early stage of continent formation. Geographical variations of the splitting parameters and their distinct dependence on direction of wave propagation through the upper mantle allow us to identify six domains of the central Fennoscandian mantle lithosphere, including the Proterozoic–Archean transition, and to model their fabrics by joint inversion of body wave anisotropic parameters. Fabrics of the Archean mantle lithosphere can be approximated by a peridotite aggregate with lineation a dipping to the NE. On the other hand, anisotropy of the Proterozoic mantle lithosphere is weaker and we model its fabric by the (a, c) foliations dipping to the SE. We present a 3D self-consistent anisotropic model of the Proterozoic and Archean upper mantle along the SW-NE profile in the south-central Finland. Boundaries of inter-growing wedges of the Proterozoic and Archean mantle lithospheres explain the longitudinal and shear wave propagation and polarization, mantle xenolith ages, surface wave tomography and location of the upper mantle reflectors. We interpret the six anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro-continents assembled. 相似文献
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Cousens BL 《The Journal of geology》2000,108(2):181-197
The geochemistry and isotope systematics of Archean greenstone belts provide important constraints on the origin of the volcanic rocks and tectonic models for the evolution of Archean cratons. The Kam Group is a approximately 10-km-thick pile of submarine, tholeiitic mafic, and subordinate felsic volcanic rocks erupted between 2712 and 2701 Ma that forms the bulk of the Yellowknife greenstone belt in the dominantly granite-metasedimentary Slave Province. Mafic rocks range from Normal-mid-ocean range basalt-like basalts to slightly light-rare-earth-element-enriched (LREE-enriched) but Nb-depleted basaltic andesites and andesites, whereas dacitic to rhyodacitic felsic rocks are strongly LREE-enriched and highly depleted in Nb. The varepsilonTNd range from +5 to -3 in the mafic to intermediate rocks and from 0 to -5.5 in the felsic rocks. The varepsilonTNd decreases with increasing La/Sm, SiO2 and decreasing Nb/La, suggesting that as the mafic magmas evolved they were contaminated by older basement rocks. Gneissic granitoids >2.9 Ga in age, found at the base of the Kam Group, have varepsilonTNd between -6 and -9 and are excellent candidates for the contaminant. The geochemical and isotopic data, combined with the submarine eruptive setting and field evidence for existing continental basement, support a continental margin rift model for the Kam Group. Similar geochemical-isotopic studies are required on other Slave greenstone belts in order to test evolutionary models for the Slave Province. 相似文献
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同位素示踪技术在地质研究中的某些应用 总被引：7，自引：0，他引：7
文中介绍了同位素示踪技术的基本原理,回顾了利用氢氧同位素示踪成矿溶液来源,研究水岩反应所取得的重要成果和最新进展;提出水岩相互作用是一个连续的演化过程,可分三个阶段,不同阶段的交换温度、水／岩比及体系的平衡、封闭情况是不一样的。以太古宙条带状硅铁建造为例,介绍了硅同位素示踪技术的新进展,证明了太古宙条带状硅铁建造为海底喷气成因,条带状构造与海底热液的周期性喷发有关。文中还介绍了氦同位素在示踪幔源组份方面的最新进展,指出我国东部油气区天然气中的氦、氩、二氧化碳等有相当一部分来自地幔;根据太平洋中部多金属结核的氦同位素组成和分布特征,提出成矿物质主要来源于海底热液活动,结核的一个圈层可能代表了一次大的海底热液活动。 相似文献
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A. A. Shchipansky 《Geotectonics》2012,46(2):122-141
The diamond-bearing mantle keels underlying Archean cratons are a unique phenomenon of Early Precambrian geology. The common
stable assemblage of the Archean TTG early continental crust and underlying subcontinental lithospheric mantle clearly shows
their coupled tectogenesis, which was not repeated in younger geological epochs. One of the least studied aspects of this
phenomenon is concerned with the eclogitic xenoliths carried up by kimberlite pipes together with mantle-derived nodules.
The eclogitic xenoliths reveal evidence for their subduction-related origin, but the Archean crustal counterparts of such
xenoliths remained unknown for a long time, and the question of their crustal source and relationships to the formation of
early continental crust remained open. The Archean crustal eclogites recently found in the Belomorian Belt of the Baltic Shield
are compared in this paper with eclogitic xenoliths from kimberlites in the context of the formation of both Archean subcontinental
lithospheric mantle (SCLM) and early continental crust. The crustal eclogites from the Belomorian Belt are identical in mineral
and chemical compositions to the eclogite nodules (group B), including their diamond-bearing varieties. The eclogite protoliths
are comparable in composition with the primary melts of the Meso- and Neoarchean oceanic crust, which was formed at a potential
temperature of the upper mantle which exceeded its present-day temperature by 150–250 K. The reconstructed pathways of the
Archean oceanic crust plunging in the upper mantle suggest that the Archean mantle was hotter than in the modern convergence
settings. The proposed geodynamic model assumes coupled formation of the Archean diamond-bearing SCLM and growth of early
continental crust as a phenomenon related to the specific geodynamics of that time controlled by a higher terrestrial heat
flow. 相似文献